This application is based on Japanese Patent Application No. 2001-251889 filed on Aug. 22, 2001, the disclosure of which is incorporated herein by reference.
The present invention relates to a vehicle air conditioner with a heat storage tank in a cooling water circuit of an engine. The heat storage tank thermally-insulates and stores high-temperature cooling water in the cooling water circuit, for heating the engine.
In a cooling water circuit described in U.S. Pat. No. 5,896,833, when an engine (i.e., internal combustion engine) starts operation, high-temperature cooling water stored in a heat storage tank is supplied to the engine, and low-temperature cooling water in the engine is stored in the heat storage tank, so that the heating capacity of the engine is improved while injurious ingredients contained in the exhaust gas are reduced. In the cooling water circuit, until the engine stops after engine-heating operation is performed, high-temperature water from the engine is introduced into the heat storage tank to be stored in the heat storage tank while low-temperature water in the heat storage tank is discharged to an outside of the heat storage tank. Accordingly, even when the temperature of cooling water (hot water) flowing from the engine is sufficiently increased after the engine-heating operation is finished, the temperature of cooling water flowing into a heater core may be decreased due to the low-temperature water discharged from the heat storage tank, and heating capacity of the heater core for heating air to be blown into a passenger compartment is decreased. Thus, air temperature heated by the heater core may be greatly reduced.
On the other hand, in a case where a vehicle is driven after being stopped for a long time, when the water stored in the heat storage tank is exchanged by high-temperature cooling water after the temperature of the engine-cooling water becomes higher, the temperature of cooling water flowing into the heater core may be decreased due to the low-temperature water discharged from the heat storage tank.
In view of the above-described problems, it is an object of the present invention to provide a vehicle air conditioner with a heat storage tank, which restricts an air temperature flowing from a heater core from being greatly reduced even when low-temperature water is discharged from the heat storage tank toward the heater core.
It is an another object of the present invention to effectively store high-temperature water in a water circuit of an engine without greatly reducing heating performance of the heater core for heating air, in a water circuit system.
According to the present invention, in an air conditioner for a vehicle having a water-cooled engine for driving the vehicle, a heater core is disposed in a water circuit for heating air to be blown into a passenger compartment of the vehicle by using the water from the engine as a heating source. A heating-amount adjustment unit is disposed to adjust the heating amount for heating air passing through the heater core. A heat storage tank is disposed for thermally-insulating and storing the introduced water from the water circuit. A water-amount adjustment unit is disposed to adjust the amount of water discharged from the heat storage tank and introduced into the heat storage tank. Finally a control unit controls the heating-amount adjustment unit and the water-amount adjustment unit. The control unit includes heating-capacity determining means for determining the heating capacity for heating air by the heater core, and discharge-amount controlling means for controlling the flow of the water discharged from the heat storage tank. In the air conditioner, when the heating-capacity determining means determines that the necessary heating capacity is smaller than a predetermined capacity during a water discharge mode for discharging the water from the heat storage tank toward the heater core, the discharge-amount controlling means controls the water-amount adjustment unit such that the flow of the water discharged from the heat storage tank becomes larger than that when the heating-capacity determining means determines that the necessary heating capacity is larger than the predetermined capacity. Accordingly, when the heating-capacity determining means determines that the necessary heating capacity is larger than the predetermined capacity in the water discharge mode, a small amount of low-temperature water, stored in the heat storage tank in a preheat mode for heating the engine using high-temperature water in the heat storage tank, flows into the heater core. Thus, the air temperature can be restricted from being greatly reduced. On the other hand, when the heating-capacity determining means determines that the necessary heating capacity is smaller than the predetermined capacity in the water discharge mode, a large amount of low-temperature water, stored in the heat storage tank in the preheat mode, flows toward the heater core. Accordingly, high-temperature water in the water circuit can be rapidly stored in the heat storage tank. Thus, the high-temperature water in the water circuit of the engine can be effectively stored in the heat storage tank without greatly reducing heating performance of the heater core in the vehicle air conditioner.
Preferably, in the water discharge mode, when the amount of air passing through the heater core is smaller than a predetermined value, the discharge-amount controlling means controls the water-amount adjustment unit such that the flow of water discharged from the heat storage tank becomes larger than that when the amount of air passing through the heater core is larger than the predetermined value. Therefore, it can effectively prevent the temperature of the water flowing into the heater core from being greatly reduced, and also prevent the air temperature from the heater core from being greatly decreased due to the low-temperature water discharged from the heat storage tank.
Alternatively, when air passes through the heater core, the heating capacity determining means determines that the necessary heating capacity is larger than the predetermined capacity, and the water discharge mode is stopped. On the other hand, when the amount of air passing through the heater core is substantially zero, the heating capacity determining means determines that the necessary heating capacity is smaller than the predetermined capacity, and the water discharge mode is performed. In this case, it can accurately prevent the water temperature flowing into the heater core from being reduced due to the low-temperature water discharge from the heat storage tank.
Further, in the water discharge mode, the flow amount of the water discharged from the heat storage tank is made larger as the water temperature flowing into the heater core becomes larger, or as the engine load becomes larger. Accordingly, the high-temperature water can be effectively stored within the heat storage tank in the water discharge mode (heat storage mode), while sufficient heating performance can be obtained in the heater core.